Rectifier
A rectifier diode steers AC into DC by blocking the negative half-cycle. It's the bulk diode in linear and offline supplies, motor controllers, and any circuit that converts wall power to DC rails.
Internally a P–N silicon junction with a thicker-than-usual depletion region for higher reverse-blocking voltage and bigger current handling. Its reverse-recovery time is slower than a Schottky, but the trade is higher voltage capability.
In plain terms
A check-valve for current — only lets flow go one way. The rectifier is the heavy-duty version, sized for power-supply input where current is high and the diode runs hot.
Why designers use it
- Build the bridge in a transformer-fed linear power supply.
- Form the input rectifier on offline AC/DC switchers.
- Catch motor-coil flyback in low-side switch drivers.
- Steer high currents in battery chargers and welders.
Best for
- Bridge rectifier
- AC-DC conversion
- Flyback catch
Key specifications
- Vf @ 1 A: 0.7 V – 1.1 V
- Reverse voltage: 50 V – 1,600 V
- Forward current: 1 A – 100 A
- Reverse recovery: 30 ns – 30 µs
- Surge (8.3 ms): 30 A – 1,000 A
When not to use it
- Where switching speed matters — pick a Schottky or fast-recovery diode.
- Where forward-drop loss matters at low voltage — Schottkys win below ~5 V rails.
Common mistakes
- Picking a 50 V diode for a 48 V rail with no margin — surges punch through.
- Skipping the snubber across each diode in a high-dV/dt switching node.
Where you will find it
- A microwave oven's high-voltage supply uses a half-wave rectifier diode rated at 12 kV and 500 mA to convert the transformer's AC output to pulsed DC: the diode must block the full peak inverse voltage of the resonant circuit, which exceeds 4000 V, without breaking down.
- A welding machine uses a full-bridge rectifier module to convert three-phase 400 V AC into DC for the welding arc: the diodes are encapsulated in a hockey-puck power module bolted to a heatsink because they pass hundreds of amperes continuously during a weld pass.
- A vintage radio's power supply uses four 1N4007 rectifier diodes in a bridge to convert mains AC to the DC that feeds the audio output stage: the slow reverse-recovery time is irrelevant at 50 Hz, and the 1000 V reverse-voltage rating gives plenty of headroom above the 325 V AC peak.
A short history
Power rectifier diodes convert AC to DC by conducting in only one direction. The earliest practical rectifiers were vacuum-tube diodes (Fleming valve, 1904); copper-oxide metal rectifiers (1920s) and selenium rectifiers (Westinghouse, 1933) dominated low-frequency power conversion through the 1930s–50s. Westinghouse and General Electric pioneered silicon p-n junction rectifiers in the 1950s, exploiting the higher voltage and current handling of silicon over selenium. The 1N4001–1N4007 series (50–1000 V, 1 A), introduced by Motorola in 1963, became the most widely produced general-purpose rectifier family. Modern fast-recovery and ultrafast diodes (FRED, soft-recovery) achieve reverse-recovery times of tens of nanoseconds, enabling high-frequency switching power supplies. Rectifier diodes remain the foundation of every AC-DC power supply in the world.
Good to know
- The 1N4001–1N4007 family (1968) is still produced by every diode maker; 1N4007 alone ships in the billions of units per year.
- Bridge rectifiers package four diodes in one part — the same 1880s circuit invented by physicist Karol Pollak still rectifies every plug-in adapter.
- Fast-recovery rectifiers (FRD) trade Vf for switching speed; they're the workhorse of the secondary side of every flyback converter.